DESCRIPTION: (Applicant's Description) The possible carcinogenic effects of a variety of birth control methods have been of public health concern and the subject of numerous epidemiologic studies during the past 3 decades. Yet, questions remain, answers to which would be of value in assessing overall risks and benefits of a variety of specific agents and procedures. An unusual opportunity to address a number of specific issues using a prospective study design is afforded by a cohort of 267,000 female textile workers in Shanghai who were recruited into a randomized trial of breast self examination in 1989-91. All women were interviewed in person on entry into the study to obtain information on their contraceptive practices and risk factor for breast cancer. We propose to match the computerized files of this cohort to two cancer registries in Shanghai to identify women who developed cancers of the breast, endometrium, ovary, cervix uteri, and liver during the first seven years of follow up (over 1.8 million women-years). Rate ratios of one or more of these cancers will be estimated, using poisson regression technique in relation to one or more of the following exposures: oral contraceptives, injectable contraceptives, tubal ligation, IUD and induced abortion. This is one of the largest cohorts of women ever assembled for epidemiologic purposes, and its location in a developing country provides an opportunity to assess carcinogenic risks of the agents and procedures of interest in a setting that differs from that of other cohort studies with respect to patterns of cancer occurrence and the presence of potentially confounding and effect modifying variables.